Variable resistance



Feb. 12, 1929. 1,702,086

s. LOEWE VARIABLE RESISTANCE Filed Sept. 1925 fwenzor: s g'muni [p l/92a fidwww Patented Feb. 12, 1929.

UNITED STATES PATENT OFFICE.

SIEGMUND LOEWE, F BERLIN, GERMANY, ASSIGNOR TO RADIO CORPORATION OF AMERICA, A CORPORATION OF DELAWARE.

VARIABLE RESISTANCE.

Application filed September 2, 1925, Serial No. 54,082, and in Germany September 11, 1924.

This invention relates to a variable resistance for wireless telegraphy and telephony and consists essentially therein that resistance elements of a high resistance value are united in a casing and in that switching instrumentalities are connected therewith, which permit a connection of the resistance elements individually or combined in parallel or in series, as well as by disconnecting some of the resistance elements.

In the accompanying drawing I have shown a perspective diagrammatic sketch of my variable high resistance unit adapted for wireless work. i

In Wireless telegraphy and telephony it had heretofore been customary to employ high resistance units possessing either a fixed resistance value, or variable high resistance units composed of a number of resistance elements, the resistance value of the unit being charged by varying the contact pressure be tween the several resistance elements, for instance by an adjustable pressure screw or the like. All heretofore known high resistance units, however, have the disadvantage that the change of the resistance value may only be accomplished with inconvenience, and in addition to this, that the range of the adjustable resistance value of the unit is insuificient for many purposes such as for receiver and audion connections, especially for instance for the grid condenser circuit employed in the latter.

My invention is based u on the discovery of the fact, that it is possib e to use a high resistance unit, having a resistance value which may be changed in steps, for the purposes of Wireless telegraphy and telephony including broad-casting. For instance I have found it to be feasible to employ resistance steps of about 500,000 ohms in order to cover a range of variable resistance between one million and three million ohms. A hi h resistance unit with a resistance value w ich may be changed in steps of such a value will be of especial importance for the. purposes of wireless telegraphy and telephony including broad-casting, especially, for instance, in audion receiving sets for the grid condenser circuits and the like.

The resistance unit according to my present invention comprises therefore a number of high resistance elements consisting preferably of a glass carrier having conducting terminals with leads thereon, said carrier being covered with a coating of soot, Chinese drawing ink or the like or also with a thin deposit of metal. The several resistance bodies or resistance elements composing the resistance unit may preferably be enclosed within a vacuum tube. Instead of such vacuum resistance elements, however, also other high resistance elements may be used, such as for instance card board strips having a dash drawn thereupon by means of Chinese drawing ink, graphite or the like, and havin the terminals of said dash connected to the eads of the resistance element.

According to my invention a plurality of such high resistance elements are united and mounted within a proper casing, and connected to proper switching instrumentalities, for instance to a rotory switch, by means of which the several resistance elements may be switched individually or in parallel for accomplishing the desired variation of the resistance unit in steps asabove indicated. If for instance the resistance elements have each a resistance value of three millions of ohms and if six such resistance elements are united with each other by a casing and a switch, a range of resistance, for instance, between three million ohms and 500,000 ohms may be covered in proper steps by connecting said resistance elements partly or wholly in parallel; in addition to this by employing partly or wholly a series connection for the several resistance elements, a resistance range up to eighteen million ohms may be covered thereby.

In the accompanying drawing I have shown an example of a high resistance unit comprising a plurality of high resistance elements, which may be switched into circuit either individually or in parallel, thus forming a resistance unit, whose resistance value may be changed in any desired plurality of steps.

The several resistance elements are designated by the numerals 1, 2 and 3 and are mounted within a casing, as shown, which is provided wit-h the terminals 4 and 5. The resistance elements 1, 2 and 3 may be connected at one of their ends with each other, theseends of the resistance elements being further connected to one of the terminals, for instance, to the terminal 5. The other poles of the resistance elements will successively come into contact with a segmentally formed I 20 device.

stance be mounted within a drum similarly to the cartridges in a revolver. Also the resistance elements may bemounted in such a manner that they may be easily exchanged, Whereby it will be possible to insert resistance elements of a difierent resistance value into the same resistance device in order to be able to produce different resistance values and different resistance steps with the same resistance I claim:

A high resistance unit for wireless telegraphy and telephony circuits comprising an insulating casing, a plurality of contacts mounted on the top ofsaid casing, a plurality of resistances each having a minimum value of three million ohms connected at one end to each of said contacts and at their other ends to a circular conductor, a lead connected to said conductor, a shaft projecting through said casing and circular conductor, a metallic plate attached to the shaft adapted to contact with one or more of said contacts on the top of said casing, means to rotate said shaft and a lead adapted to contact electrically with said shaft.

I In testimony whereof I have affixed my signature.

'SIEGMUND LOE-WE. 

